Monitoring the induction of trichothecene mycotoxins of Fusarium graminearum using GFP during wheat head infection and in culture

The fungal pathogen Fusarium graminearum is the most common agent of Fusarium Head Blight (FHB) in small grain cereals and of cob rot in maize. The threat posed by this fungus is due to a decrease in yield and mycotoxin contamination in the harvested cereals. It has been shown that trichothecenes influence virulence of Fusarium graminearum in a highly complex manner, which is strongly host as well as moderately chemotype specific. To evaluate the induction of the trichothecene pathway the GFP gene was fused to the Tri5 promoter and integrated into the genome by homologous integration. The resulting mutants exhibit GFP driven by the endogenous Tri5 promoter and a fully functional Tri5 gene. As tri5 encodes for the trichodiene synthase which is the key enzyme in the pathway we are now able to monitor the induction of trichothecenes under real time conditions. To simplify the localisation of the fungus in plant tissue and in culture dsRed was integrated under constitutive control of the gpd promoter. We will show: first of all, induction of GFP in the mutant strain reflects Tri5 induction and DON production in the wild type; secondly, induction of Tri5 is tissue specific during infection of wheat; and thirdly, Tri5 is inducible during growth in culture.